The present invention relates generally to frequency determination and more specifically to determining whether the frequency of an input signal exceeds a reference frequency or falls below a possibly different reference frequency.
In certain applications, it is desirable to determine whether the frequency of an input signal exceeds a predetermined reference frequency or falls below another possibly different predetermined reference frequency. Such a determination can be adapted for use to control other circuitry in response to the frequency of the input signal. For example, a frequency determination circuit can be adapted to control, in response to the frequency of an input signal, the amount of power supplied to an air conditioning unit, a lamp, or a computer peripheral such as a display monitor or a printer. In other contexts, a frequency determination circuit can be adapted to monitor the frequency of an input signal, and to inform the user, through means perceptible to the human senses, of the status of the input signal.
It has long been recognized in the production of electronic circuits that production costs are directly correlated with circuit complexity. Thus, there is desired a simple, inexpensive circuit which can determine whether the frequency of a given input signal exceeds a certain frequency threshold or falls below another possibly different frequency threshold, and can output a control signal and/or notify the human operator in response to that determination.